It’s hard to say which fan base will be more disoriented. Yankees fans will have to bury a decade of bile when their new third baseman steps in the batter’s box. Red Sox fans will have to watch their heart and soul come back in pinstripes.

On second thought, it’s not that hard to see which side will need more therapy.

For Boston, this must feel like a fastball to the head. The kind Joba Chamberlain used to throw at the glaring Youkilis. The only thing worse would have been if the Sox got A-Rod back in the deal and Bobby Valentine was rehired as manager.

From a baseball standpoint, signing the 33-year-old actually represents a youth movement for the Yankees. Youkilis isn’t what he used to be, but he’ll help keep the charade going one more season in the Bronx.

Yankees fans will just have to convince themselves that Youkilis is not Boston’s version of the Manchurian Candidate out to destroy what’s left of the Evil Empire. If that’s hard, they just have to recall Yanks-Sox history.

New York has been raiding Boston’s shelves since Babe Ruth took the dynasty with him 90 years ago. Sparky Lyle, Wade Boggs, Roger Clemens and Johnny Damon all made their way south. Seven members of Boston’s beloved 2004 World Series team became Yankees.

Who’s the best ex-Yank in Boston?

Elston Howard was traded there at the tail end of his career. Bob Turley? David Cone? Boston should just be happy George Steinbrenner didn’t steal the Old North Church and install it in Monument Park.

It’s never been a two-way street, but Youkilis is like a big, bald semi barreling south. Red Sox fans can pretend this one doesn't hurt any worse than the others, but they know better.

They could consider Damon, Clemens and Boggs turncoats for voluntarily blowing town. They could make fun of Damon’s arm and hair. Youkilis won’t have to worry about his head adhering the Yankees’ dress code.

He left Boston a martyr after Valentine jerked him around. When he returned with the White Sox, Fenway Park greeted him with a standing ovation.

Why not? Youk helped break the Curse of the Bambino in ’04. He married Tom Brady’s sister. He looked and played like a blue-collar Boston guy.

When the TV show “Man v. Food” was in Boston, host Adam Richman went to Eagle’s Deli. Richman goes to local hangouts and tries to devour the most imposing menu item. At Eagle’s Deli, it was 12 pounds of burgers, cheese, bacon and French fries. That’s more food than even Josh Beckett could eat during an entire game.

So Richman, a New Yorker, challenged a huge guy named Chris to see who could eat more in 30 minutes. If Richman lost, he’d have to put on a Boston T-shirt and have his picture taken for the restaurant’s Wall of Shame.

Who should be sitting at the next table?

“That's how you eat a burger?” Youkilis asked Richman. “You bum!”

Youk helped the cause by eating a couple of Chris’ French fries. The hometown boy ended up winning, and as the food flew, diners started chanting “Yankees Suck! Yankees Suck!” at Richman.

“Now he knows how I feel when I go to New York City,” Youkilis said.

New York City now will know how it feels to cheer for a third baseman who doesn’t try to get women’s phone numbers during games.

Don’t worry, Yankees fans. You’ll adjust. If you doubt that, you can take comfort in one thing: If the sight of Youkilis in pinstripes is hard to swallow, just think how the people at Eagle’s Deli are going to feel.